[Bug middle-end/128004] wrong code with -frounding-math: 1.0 + -1.0 is folded to +0.0 under FE_DOWNWARD

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128004

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2026-10-20
                 CC|                            |sayle at gcc dot gnu.org

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  The const_binop condition is

      /* Don't constant fold this floating point operation if the
         result may dependent upon the run-time rounding mode and
         flag_rounding_math is set, or if GCC's software emulation
         is unable to accurately represent the result.  */
      if ((flag_rounding_math
           || (MODE_COMPOSITE_P (mode) && !flag_unsafe_math_optimizations))
          && (inexact || !real_identical (&result, &value)))
        return NULL_TREE;

but that does not consider the case of signed zero.